661718694 has 192 divisors, whose sum is σ = 1783756800. Its totient is φ = 159134976.

The previous prime is 661718683. The next prime is 661718699. The reversal of 661718694 is 496817166.

It is a happy number.

It is a hoax number, since the sum of its digits (48) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661718699) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 8376147 + ... + 8376225.

It is an arithmetic number, because the mean of its divisors is an integer number (9290400).

Almost surely, 2^661718694 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661718694, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (891878400).

661718694 is an abundant number, since it is smaller than the sum of its proper divisors (1122038106).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661718694 is a wasteful number, since it uses less digits than its factorization.

661718694 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179 (or 156 counting only the distinct ones).

The product of its digits is 435456, while the sum is 48.

The square root of 661718694 is about 25723.8934455887. The cubic root of 661718694 is about 871.4138696052.

The spelling of 661718694 in words is "six hundred sixty-one million, seven hundred eighteen thousand, six hundred ninety-four".